This invention relates to computing devices, and more particularly to computer memory systems.
Today""s computer systems, notably server and workstations, have large system memory banks. The memory bank is a group of modules that make up a logical memory unit. This type of design permits the computer system to be easily upgraded with more memory, and permits failed modules to be easily replaced.
In conventional computer systems, when a memory module fails, it is necessary to power down the entire computer system. This results in down time and the contents of the memory may be lost.
To prevent loss of data when system memory fails, many systems use xe2x80x9cmirroringxe2x80x9d techniques. This requires a doubling of memory capacity, and is an expensive and space-consuming solution.
In connection with memory systems, data recovery schemes have been associated with transfer of data from memory to the processor. A technique originally developed for recovering data on a failed disk drive has been applied in this context. More specifically, RAID (redundant array of inexpensive disks) techniques have been used to provide multiple channels for carrying data from memory to the processor. RAID techniques are used to stripe data across multiple channels and to calculate and transfer parity data with the original data. This method providing data transfer is described in U.S. Pat. No. 5,463,643, to Gaskins, et al., assigned to Dell USA, L.P.
One aspect of the invention is a memory system for a processor-based computer system. The system memory is arranged as a set of memory modules, each capable of receiving portion of a larger block of data. For example, the memory modules may be DIMMs. A logic unit is programmed to calculate parity data associated with a input data to be stored in the memory modules. It adds the parity data to the input data to form a block of data, and distributes the block of data among the memory modules. If a memory module fails, the logic unit may be called upon to calculate recovery data. The memory modules are connected to power in a manner that permits them to be xe2x80x9chot pluggedxe2x80x9d, that is, removed without affecting operation of the rest of the computer system.
An advantage of the invention is that it provides for data recovery of data stored in system memory, without the need for duplicate storage that would be required for complete data redundancy. All that is required is the addition of hardware logic for parity-based data recovery calculations, and sufficient memory for storing parity data.